The aim of this study is to test a key problem in cardiovascular epidemiology: Does systematic change in sodium intake -- stepwise over a range reasonable for the general population (30, 60, 90 compared to 110 mEq per day) -- influence group mean blood pressure of a population of healthy high school students? This intervention study on the problem of Na intake as a risk factor for high blood pressure is to be done at a Seventh Day Adventist boarding high school, where a single cafeteria -- under health conscious and nutritionally trained leadership -- serves all meals consumed by the students. This makes possible the planned design, involving 2-3-group cross-over experiments of the metabolic-ward-type, modelled after the methodology used with great success to elucidate relationships between dietary lipids, etc. and serum cholesterol (e.g., by Anderson, Grande, Keys; Conner, et al. Hegsted, et al.; Mattson, et al.). Based on informed consent of the school headmaster, director of food services, Board, students and parents, volunteers are to be randomly assigned to experimental and control groups for a 24-48-day period, followed by cross-over for the next 24-48-days. In the first trial two groups, experimental and control, are for 24 days to consume diets of mixed ordinary foods containing 60 and 110 mEq Na per person per day respectively (the latter the estimated usual level in the students' lacto-ovo-vegetarian daily diet at the School). Aside from the differences in Na level, the two diets are to be identical in macro- and micro-nutrient content and types of foods fed. Diets are to be serially assessed by three complementary methods -- food disappearance, 3-day food records, and biochemical anaylses of duplicate meals, plus assessment of plate waste, weight, and 24-hour urine Na, K and creatinine serially. At baseline and serially, multiple BP readings per student are to be made by trained certified technicians using regular Hg sphygmomanometers and the random-zero device, and by a pre-tested automated electronic instrument (the Vita Stat).